refactor: "hypotenuse" is normalization

packages/entity/traits/mobile.js

@@ -34,7 +34,7 @@ class MobileBase extends Trait {
           return;
         }
         this.requestedMovement = Vector.scale(
-          Vector.hypotenuse(vector),
+          Vector.normalize(vector),
           this.speed
         );
         this.entity.emit('movementRequest', this.requestedMovement);

packages/math/vector/index.js

@@ -146,28 +146,20 @@ export function dot(l, r) {
   return l[0] * r[0] + l[1] * r[1];
 }
 
-// Get a hypotenuse unit vector. If an origin vector is passed in, the
-// hypotenuse is derived from the distance to the origin.
+// Get a unit vector.
 //
-//     avocado> Vector.hypotenuse [5, 5], [6, 7]
-//     [-0.4472135954999579, -0.8944271909999159]
-//
-//     avocado> Vector.hypotenuse [.5, .7]
+//     avocado> Vector.normalize [.5, .7]
 //     [0.5812381937190965, 0.813733471206735]
-export function hypotenuse(unitOrDestination, origin) {
-  let distanceOrUnit = origin ?
-    sub(unitOrDestination, origin)
-  :
-    unitOrDestination;
-  const dp = dot(distanceOrUnit, distanceOrUnit);
+export function normalize(v) {
+  const dp = dot(v, v);
   if (0 === dp) {
     return [0, 0];
   }
-  const hypotenuse = scale(distanceOrUnit, 1 / Math.sqrt(dp));
+  const normalized = scale(v, 1 / Math.sqrt(dp));
   // Don't let NaN poison our equations.
   return [
-    NaN === hypotenuse[0] ? 0 : hypotenuse[0],
-    NaN === hypotenuse[1] ? 0 : hypotenuse[1],
+    NaN === normalized[0] ? 0 : normalized[0],
+    NaN === normalized[1] ? 0 : normalized[1],
   ];
 }
 
@@ -222,15 +214,15 @@ export function isNull(v) {
   return 0 === v[0] || 0 === v[1];
 }
 
-export function overshot(position, hypotenuse, destination) {
+export function overshot(position, normal, destination) {
   const overshot = [false, false];
   for (const i = 0; i < 2; ++i) {
-    if (hypotenuse[i] < 0) {
+    if (normal[i] < 0) {
       if (position[i] < destination[i]) {
         overshot[i] = true;
       }
     }
-    else if (hypotenuse[i] > 0) {
+    else if (normal[i] > 0) {
       if (position[i] > destination[i]) {
         overshot[i] = true;
       }
@@ -252,7 +244,7 @@ export function overshot(position, hypotenuse, destination) {
 //     avocado> Vector.toDirection4 [1, 0]
 //     1
 export function toDirection4(vector) {
-  vector = hypotenuse(vector);
+  vector = normalize(vector);
   const x = Math.abs(vector[0]) - SQRT_2_2;
   if (x > 0 && x < SQRT_2_2) {
     return vector[0] > 0 ? 1 : 3;
@@ -283,7 +275,7 @@ export function angle(v) {
 //     avocado> Vector.toDirection8 [1, 0]
 //     1
 export function toDirection8(v) {
-  v = hypotenuse(v);
+  v = normalize(v);
   // Orient radians.
   let rad = (TWO_PI + angle(v)) % TWO_PI;
   rad = (rad + HALF_PI) % TWO_PI;
@@ -325,10 +317,10 @@ export function fromDirection(direction) {
     case 1: return [1, 0];
     case 2: return [0, 1];
     case 3: return [-1, 0];
-    case 4: return hypotenuse([1, -1]);
-    case 5: return hypotenuse([1, 1]);
-    case 6: return hypotenuse([-1, 1]);
-    case 7: return hypotenuse([-1, -1]);
+    case 4: return normalize([1, -1]);
+    case 5: return normalize([1, 1]);
+    case 6: return normalize([-1, 1]);
+    case 7: return normalize([-1, -1]);
   }
 }
 
@@ -343,7 +335,7 @@ export function interpolate(ultimate, actual, easing = 0) {
   return add(
     actual,
     scale(
-      hypotenuse(ultimate, actual),
+      normalize(ultimate, actual),
       magnitude / easing
     )
   );

packages/math/vector/index.spec.coffee

@@ -29,11 +29,11 @@ describe 'Vector', ->
 
     expect(Vector.dot [2, 3], [4, 5]).toEqual 23
 
-    expect(Vector.hypotenuse [5, 5], [6, 7]).toEqual [
+    expect(Vector.normalize [5, 5], [6, 7]).toEqual [
       -0.4472135954999579, -0.8944271909999159
     ]
 
-    expect(Vector.hypotenuse [.5, .7]).toEqual [
+    expect(Vector.normalize [.5, .7]).toEqual [
       0.5812381937190965, 0.813733471206735
     ]